Page:Popular Science Monthly Volume 30.djvu/250

236 Cuban climate, Iceland comes down upon us from an open window. Especially is this likely to occur in school-houses, where children will instinctively seek to get a breath of fresh air that has not had all its natural refreshing qualities quite cooked out of it by hot stoves, furnaces, or steam-pipes. And all these sudden changes and shocks of cold come upon us while the whole system has its vitality and powers of resistance gauged down to the low necessities of a tropical climate.

And what should we expect as the effect upon the health&mdash;upon the respiratory organs? What are the facts? Pneumonia has increased nearly threefold in New York, in proportion to the population, within the last fifty years; and, if we had separate records for that class who most use the hot-air arrangements, we probably would find a much greater increase.

Bronchitis, which is also getting to be a very prevalent and fatal disease, has increased even more rapidly than pneumonia, and now causes about fifteen hundred deaths in New York city every year, being an increase of nearly fivefold to the population in fifty years. What is the cause? We have a sufficient and a very obvious cause, in the fact that in our methods of heating our houses we have been "progressing backward." Fifty years ago there were few furnaces or close stoves, and no steam-pipes, for warming; houses were warmed by open fires. The difference is radical and of great importance.

It may be briefly explained thus: Radiant heat from the sun or from an open fire passes through the air (so far as it is pure air) without warming it; that is to say, without being obstructed or retained by it (just as light does), and only warms the pavement, floor, walls, or other opaque body on which it falls. Hence, on a sunny day the pavement will be at 100°, while the air above it is only 50°. The air that touches the iron bars or the surface of the fire in an open grate goes to feed the fire, and then is drawn up the chimney. Only pure, radiant heat is thrown into the room, not hot air; and it does not heat the air at all directly, but warms our bodies, the walls, furniture, etc.

Recently we have thrown this aside, and, instead, put a surface of hot iron in the room or in the cellar, in the form of stove or furnace, or steam-pipes, or hot-water pipes, against which the air itself is heated by convection or contact, and by its consequent lightness rises into the room and to the ceiling.

By the first method&mdash;open radiation&mdash;we warm our bodies, walls, floor, furniture; by the second we heat the air. By the first method all the heat the air gets it gets from floor, walls, and furniture. By the second, all the heat the floor, walls, and furniture get they get from the air, the process being exactly the reverse. The difference is radical and great.

By radiation from sun or open fire we get a quick, active heat,